1. Field of the Invention
The present invention relates to a transistor, and in particular, to an extremely small transistor which can correspond to significant reduction in the size of an electronic circuit.
2. Description of the Related Art
There is a limit to the degree of integration of a silicon device which is now widely used in view of its working. If a gate width of a silicon field effect transistor is 100 nm or less, the transistor is considered to be extremely difficult to use industrially. Also, if it is thought that, as a principle, if the gate width of a transistor is 20 nm or less, an operation of the transistor becomes unstable because of a tunnel effect or the like. Accordingly, a molecular device which uses a functional molecule itself such as carbon nanotube, Fullerene or the like is being developed as an electronic device material for replacing silicon.
Meanwhile, a function of deoxyribonucleic acid (which may be appropriately referred to as xe2x80x9cDNAxe2x80x9d hereinafter) has attracted attention. Deoxyribonucleic acid is a substance which has a double helix structure and is formed of pairs of two bases selected from four kinds of bases including adenine, cytosine, guanine and thymine, on a ribose phosphate chain. A natural DNA has a diameter of around 2 nm and a length of a few meters. DNA exists within nuclei of cells of various organisms. All genetic information is recorded by a DNA sequence. The specific chemical structure of DNA was discovered by Watson and Crick. Thereafter, human genome and enzyme generation has been researched by studying DNA sequence.
Use of DNA as materials for an electronic device has been studied and electric conductivity of DNA especially has attracted attention.
If it is possible to use DNA on an electronic circuit, it is considered that a degree of integration which exceeds that of a conventional silicon device circuit can be accomplished by using DNA as a component of a small circuit. However, an operation example of a DNA transistor has not been reported so far.
An object of the present invention is to provide extremely small transistor which can correspond to significant reduction in the size of an electronic circuit by using DNA as structural materials. The present invention discloses a transistor comprising a source electrode member; a drain electrode member; a gate electrode member; and a deoxyribonucleic acid molecule or a deoxyribonucleic acid molecule aggregate, wherein at least one of said source electrode member, said drain electrode member and said gate electrode member connects to said deoxyribonucleic acid molecule or deoxyribonucleic acid molecule aggregate.
In the transistor of the present invention, since a deoxyribonucleic acid molecule or a deoxyribonucleic acid molecule is used as a part of structural materials, the transistor can be extremely small, and correspond to significant reduction in the size of an electronic circuit.
There are two aspects of the transistor of the present invention in view of a function of the deoxyribonucleic acid molecule (DNA) or deoxyribonucleic acid molecule aggregate.
(1) An aspect characterized in that DNA or deoxyribonucleic acid molecule aggregate acts as a carrier transporting material,
(2) An aspect characterized in that DNA or deoxyribonucleic acid molecule aggregate is in a form of mass to connect to a gate electrode member, and the mass has a function of an insulating material.
In accordance with aspect (1), preferably said electrode members are rod-like shape, and said source electrode member, said gate electrode member and said drain electrode member are arranged in that order in a longitudinal direction of connects of said deoxyribonucleic acid molecule or deoxyribonucleic acid molecule aggregate.
In the aspect (1), preferably said gate electrode member has a portion connecting to said deoxyribonucleic acid molecule or deoxyribonucleic acid molecule aggregate, the portion having a width from 0.1 nm to 100 nm. Further, a gap between a point where said source electrode member connects to said deoxyribonucleic acid molecule or deoxyribonucleic acid molecule aggregate and a point where said drain electrode member connects to said deoxyribonucleic acid molecule or deoxyribonucleic acid molecule aggregate is 1 nm to 100 nm. Preferably, said deoxyribonucleic acid molecule or deoxyribonucleic acid molecule aggregate has a length of 2 nm to 10 xcexcm. Further, said deoxyribonucleic acid molecule or deoxyribonucleic acid molecule aggregate has 10 or less molecules, and is thread-like or bundle-like.
In accordance with the aspect (1), a transistor of the present invention can operate as a single electron tunneling transistor as well as an ordinary field effect transistor by using DNA.
In accordance with aspect (2), a deoxyribonucleic acid molecule or deoxyribonucleic acid molecule aggregate is disposed so as to contact a carrier transporting material, a gate electrode member contacts a deoxyribonucleic acid molecule or deoxyribonucleic acid molecule aggregate so as not to contact the carrier transporting material, a source electrode member and a drain electrode member connect to the carrier transporting material while sandwiching a deoxyribonucleic acid molecule or deoxyribonucleic acid molecule aggregate therebetween.
In accordance with the aspect (2), a gap between a point where said source electrode member which connects to said carrier transporting material and a point where said drain electrode member which connects to said carrier transporting material is 1 nm to 1 xcexcm. Further, in the aspect (2), the carrier transporting material is preferably a nanotube. In accordance with the aspect (2), a thickness of the mass of deoxyribonucleic acid molecules or deoxyribonucleic acid molecule aggregate is preferably 2 nm to 100 nm.
In the aspects (1) and (2), the number of bases composing the deoxyribonucleic acid molecule or the deoxyribonucleic acid molecule of the deoxyribonucleic acid molecule aggregate is preferably 2 to 100,000.
In the aspects (1) and (2), because DNA is extremely fine, it is difficult for effective electric wiring to be applied thereto, However, if a carbon nanotube is used for electrode members, it is easy to apply electric wiring to DNA. That is, a carbon nanotube is preferable for the gate electrode, the gate electrode and/or the drain electrode.